1. Technical Field
The present invention relates to a display device for a vehicle which displays visible information in the form of a virtual image.
2. Background Art
As for display devices for vehicles, head-up display (HUD) devices which are high in viewability may be used for allowing drivers to quickly recognize, for example, information that is high in urgency though small in information amount.
In general, in vehicular head-up display, an optical image containing visible information displayed on a display unit of a display device main body is projected so as to be guided to the windshield of a vehicle or a light reflection member called a combiner and an image of resulting reflection light is projected so as to be seen by the eyes of the driver.
As a result, when looking ahead in an ordinary driving posture, the driver can visually recognize the visible information projected by the head-up display together with a scene ahead and part of the body of the self vehicle that are seen through the windshield. A virtual image of visible information to be visually recognized by the driver is formed at a position that is distant forward from the surface of the windshield, for example, at a position that is distant from the viewing point by about several meters. Therefore, during driving, the driver can recognize information displayed by the head-up display at the same time as a scene ahead without his or her eyes' having to making focus adjustments.
In general, the device main body of such a head-up display device is disposed inside an instrument panel of the vehicle. And light of visible information that is displayed on the display unit located inside the device main body is projected toward a projection area of the windshield, the combiner, or the like via an optical path including a reflection member such as a mirror of an expansion system, whereby a virtual image is formed at a position that is distant from the viewing point of the driver by a prescribed distance.
Prior art techniques relating to vehicular head-up display devices are disclosed in JP-A-11-72742, JP-UM-A-1-68938, and JP-A-9-109732.
The head-up display disclosed in JP-A-11-72742 has such a structure that a projection combiner is incorporated in the device main body and can be developed and accommodated. That is, when the head-up display is used, the combiner is developed so as to be erected in a prescribed direction so as to be able to project an optical image toward the field of view of the driver. When the head-up display is not used, the combiner can be accommodated so as not to obstruct the view of the driver. Supported by a rotation shaft, the combiner can be developed or accommodated by rotating and displacing it.
As for the head-up display disclosed in JP-UM-A-1-68938, a structure is proposed which allows a combiner to slide in the top-bottom direction (i.e., the direction perpendicular to the thickness direction). This structure allows the combiner to move to such a position that the head-up display is usable and to escape to a position where it does not obstruct the view of the driver.
JP-A-9-109732 discloses a structure which allows a combiner (transparent reflection plate) capable of being used in a head-up display to be displaced into an erected use state or an inclined accommodated state.
Incidentally, in vehicles such as automobiles, when the intensity of external light such as sunlight is high, strong light passes through the windshield and shines on the instrument panel. Furthermore, light reflected from the surface of the instrument panel may be reflected by the surface of the windshield and projected toward the field of view of the driver.
As a result, not only a scene ahead such as a road but also a superfluous virtual image (ghost) produced by reflection from the surface of the instrument panel exists in the field of view of the driver and may obstruct driving (e.g., dazzle the driver). In view of this, in many cases, the surface of the instrument panel is treated properly so as to less likely produce a ghost.
On the other hand, in vehicles equipped with a head-up display, a ghost may occur due to the presence of a combiner (described above). That is, external light such as sunlight passes through the windshield and shines on the head-up display that is disposed in the vicinity of the surface of the instrument panel. And reflection light from the surface of the instrument panel is reflected by the surface of the windshield and projected toward the field of view of the driver. As a result, a virtual image (ghost) of part of the head-up display goes into the eyes of the driver and obstructs driving.
There are no prior art techniques in which particular countermeasures are taken against a superfluous ghost that is produced by a head-up display. In particular, combiners that are configured so as to be movable are currently in such a situation that even if a certain countermeasure is taken, formation of a superfluous ghost due to reflection of external light by a member of the combiner cannot be avoided when the combiner is in a certain state (in terms of position, inclination, or the like).
The present invention has been made in the above circumstances, and an object of the invention is therefore to provide a display device for a vehicle which can suppress formation of a superfluous ghost due to reflection of external light even in the case where a combiner is used that is configured so as to be movable.
To attain the above object, the display device for a vehicle according to the invention has features that are expressed as the following items (1)-(9):
(1) A display device for a vehicle which has a display unit for displaying visible information and which reflects with a combiner and projects, toward a prescribed observation region, light carrying visible information to be displayed on the display unit to display the visible information in a form of a virtual image, the display device comprising:
a deploying and accommodating mechanism configured to change a state of disposition of the combiner between a position of a use state in which a display can be seen in the observation region and a position of an unused state in which a display cannot be seen in the observation region,
wherein the deploying and accommodating mechanism includes a restricting unit configured to restrict an inclination, with respect to a prescribed direction, of a surface of the combiner to a predetermined angle of a ghost suppression state at least when the combiner is located at the position of the use state.
(2) The display device for the vehicle according to item (1), wherein the deploying and accommodating mechanism includes a slide mechanism which can move the combiner parallel with the surface of the combiner in a vertical direction while the inclination of the surface of the combiner is kept at the angle of the ghost suppression state.
(3) The display device for the vehicle according to item (1), wherein the deploying and accommodating mechanism includes an angle adjusting mechanism configured to adjust the inclination of the surface of the combiner between the angle of the ghost suppression state and an angle of an escape state in which the surface of the combiner is approximately located in a horizontal direction.
(4) The display device for the vehicle according to item (3), further comprising:
a light reflection suppressing cover capable of covering a surface, opposite to a projection surface, of the combiner; and
a cover escape mechanism capable of causing the light reflection suppressing cover to escape to a position that is distant from the combiner at least when the combiner is located in the angle of the ghost suppression state.
(5) The display device for the vehicle according to item (4), wherein the deploying and accommodating mechanism includes a first drive unit configured to adjust the inclination of the surface of the combiner and a second drive unit configured to adjust at least the inclination of the light reflection suppressing cover.
(6) The display device for the vehicle according to item (5), wherein the second drive unit includes, as guide grooves for restricting movement of the light reflection suppressing cover, a rotation groove which is engaged with a first portion of the light reflection suppressing cover and guides the light reflection suppressing cover in its rotation direction and a pull-in groove which communicates with the rotation groove, is engaged with a second portion of the light reflection suppressing cover, and guides the light reflection suppressing cover in a direction that is parallel with its surface.
(7) The display device for the vehicle according to item (4), wherein the deploying and accommodating mechanism includes a first drive unit configured to adjust the inclination of the surface of the combiner and a second drive unit configured to adjust the position of the light reflection suppressing cover between a position for covering the combiner and a position of escape from the combiner;
wherein the light reflection suppressing cover is deformable; and
wherein the second drive unit has a wind-up mechanism which is connected to a bottom end of the light reflection suppressing cover.
(8) The display device for the vehicle according to item (7), wherein side end portions of the combiner are formed with guide grooves for restricting a movement range of the light reflection suppressing cover so that the light reflection suppressing cover can move only parallel with the surface of the combiner.
(9) The display device for the vehicle according to any one of items (1) to (8), further comprising:
an optical path bending mirror which is disposed on an optical path between the display unit and the combiner.
According to the display device for a vehicle having the configuration of item (1), the inclination of the surface of the combiner is restricted in the use state. Therefore, a phenomenon that external light produced by the combiner itself or its vicinity goes toward the viewing point of the driver can be suppressed, whereby formation of a superfluous ghost can be prevented.
According to the display device for a vehicle having the configuration of item (2), the inclination of the surface of the combiner can be kept at the restriction angle even when or after the combiner is accommodated, as a result of which formation of a superfluous ghost can always be prevented.
According to the display device for a vehicle having the configuration of item (3), the space that is necessary for housing the combiner can be reduced, whereby the capacity of the display device itself for a vehicle and the space in the vehicle that is necessary for its installation can be reduced.
According to the display device for a vehicle having the configuration of item (4), the light reflection suppressing cover suppresses reflection of external light when the combiner is accommodated. Therefore, formation of a superfluous ghost can always be prevented. Furthermore, when the combiner is used, the light reflection suppressing cover escapes to expose the back side of the combiner. As a result, the driver can see, for example, a scene ahead (i.e., on the back side of the combiner) that is carried by light passing through the combiner.
According to the display device for a vehicle having the configuration of item (5), the inclination of the surface of the combiner and the inclination of the light reflection suppressing cover can be adjusted by the respective drive units which are independent of each other. Therefore, the inclinations can easily be adjusted to proper angles.
According to the display device for a vehicle having the configuration of item (6), the inclination of the light reflection suppressing cover and its advance/retreat position in the direction parallel with its surface can be adjusted by a simple control. Furthermore, the space that needs to be secured for escape of the light reflection suppressing cover can be reduced, whereby the capacity of the display device itself for a vehicle and the space in the vehicle that is necessary for its installation can be reduced.
According to the display device for a vehicle having the configuration of item (7), the light reflection suppressing cover can easily be moved to the position of the state in which to cover the opposite side of the combiner and the position of the escape state. Furthermore, the space that needs to be secured for escape of the light reflection suppressing cover can be reduced, whereby the capacity of the display device itself for a vehicle and the space in the vehicle that is necessary for its installation can be reduced.
According to the display device for a vehicle having the configuration of item (8), the light reflection suppressing cover can be prevented from being deformed and thereby lifting up from the surface of the combiner. Therefore, reflection of light from the back surface of the combiner can be suppressed and hence formation of a superfluous ghost can be prevented.
According to the display device for a vehicle having the configuration of item (9), the optical path from the display unit to the combiner can be elongated without increasing the size of the device body. As a result, the distance from the viewing point of the driver to the position of a displayed virtual image can be made long without increasing the magnification of the optical system.
The invention makes it possible to suppress formation of a superfluous ghost due to reflection of external light even in the case where a combiner is used that is configured so as to be movable. That is, even where a head-up display is used, the invention can make formation of a driving-obstructing superfluous image less likely and thus serves for safe driving.
The invention has been described above in a simplified manner. The details of the invention will become more apparent when the modes for carrying out the invention which will be described below are read with reference to the accompanying drawings.